1. Field of the Invention
The present invention relates to a method of forming a patterned thin film and a method of fabricating a micro device in which a patterned thin film is formed through dry etching.
2. Description of the Related Art
For micro devices incorporating a thin film formed into a specific pattern (called a patterned thin film in this application), one of methods for forming the patterned thin film is to employ dry etching. A micro device means a small-size device fabricated through the use of thin-film forming techniques. Examples of micro devices include semiconductor devices, thin-film magnetic heads, transducers and actuators incorporating thin films.
Conventional methods for forming a patterned thin film having a narrow groove through dry etching include the one disclosed in Published Unexamined Japanese Patent Application (KOKAI) Heisei 8-78414 (1996). This method will now be described briefly with reference to FIG. 28 to FIG. 33.
In this method, first, as shown in FIG. 28, an etching stopper film 302 and a film 303 to be patterned are formed in this order on a base layer 301 as a substrate through sputtering or the like. Next, as shown in FIG. 29, an etching mask layer 304 is formed through sputtering or the like on the film 303 to be patterned.
Next, as shown in FIG. 30, a patterned photoresist layer 305 is formed on the etching mask layer 304 through photolithography. The photoresist layer 305 has an opening 305a at a position corresponding to a groove that will be formed later in the film 303.
Next, as shown in FIG. 31, the etching mask layer 304 is selectively etched through dry etching such as reactive ion etching and ion milling using the photoresist layer 305 as a mask. Next, as shown in FIG. 32, the photoresist layer 305 is removed through the use of a solvent or through ashing. The etching mask layer 304 is thereby patterned, and an etching mask 306 to be used for patterning the film 303 is thus obtained.
Next, as shown in FIG. 33, the film 303 is selectively etched through, for example, reactive ion etching using the etching mask 306. The film 303 is thereby patterned into a patterned thin film 307 having a groove 307a. 
Incidentally, as shown in FIG. 34, when another thin film 308 is formed on the patterned thin film 307 during the fabrication process of a micro device, there are cases where the thin film 308 need to adhere to end portions 307b of the patterned thin film 307 as well, the end portions facing the groove 307a. The thin film 308 may be an interlayer insulation film, for example.
However, in the case of the patterned thin film 307 formed by the method shown in FIG. 28 through FIG. 33, the end portions 307b are formed to be almost vertical with respect to the top surface of the base layer 301. In this case, as shown in FIG. 34, there arises a problem that the thin film 308 adhering to the end portions 307b is small in volume. Where the thin film 308 is to serve as an interlayer insulation film, an insulation failure may occur if the film 308 adhering to the end portions 307b is too small in volume.
For the patterned thin film 307 formed by the method shown in FIG. 28 through FIG. 33, on the other hand, the width of the groove 307a depends on the width of the opening 305a in the photoresist layer 305 patterned through photolithography. This poses an optical limit for attaining a smaller width of the groove 307a, that is, the width of the groove 307a cannot be reduced beyond this limit.